Relaxation and crimp stabilization of acrylonitrile polymer fibers through treatment with aqueous solutions of acetonitrile, pyridine or dioxane



Nov; 14, 1967 YOSHIMASA FUJlTA ET AL RELAXATION AND CRIMP STABILIZATION OF ACRYLONITRILE POLYMER FIBERS THROUGH TREATMENT WITH AQUEOUS SOLUTIONS OF ACETONITRILE, PYRIDINE OR DIOXANE Filed 001;. 9, 1965 30 50% Q 20 r U) 0 l l I L 20 40 60 a0 /00. ACETO/V/T/P/LE CONCENTRAT/ON (%1 30- 95 0 m g t 5g /0- a0 "0 0 I I l 1 PYR/Dl/VE CONCENTRAT/ON 1%) g 20 a0=c 1 /0 0 YOSH/MASA F3 5;?

20 40 m0 NOBUH/HO rsu rsu/ D/OXANE CONCENTRATION rl- -z United States Patent 3,352,626 RELAXATION AND CRIMP STABILIZATION OF ACRYLONITRILE POLYMER FIBERS THROUGH 'I'REATMENT WITH AQUEOUS SOLUTIONS OF ACETONITRILE, PYRIDINE OR DIOXANE Yoshirnasa Fujita and Nobuhiro Tsutsui, Okayama, Japan, assignors to American Cyanamid Company, Stamford, Conn., a corporation of Maine Filed Oct. 9, 1963, Ser. N 315,023 Claims priority, application Japan, Oct. 12, 1962, 37/ 45,342 8 Claims. (Cl. 8130.1)

This invention relates to a novel method for shrinking or relaxing fibers, yarns, or fabrics made of acrylonitrile type polymers. This invention is particularly suitable for setting the crimps in fibers, yarns, and fabrics of acrylonitrile type polymers.

Generally speaking, crimps play an important role in giving fibers a superior yarn quality and bulkiness and improving the hand of'textile fabrics. In the case of acrylonitrile type fibers also, it is known to impart a crimp to the fiber during its manufacture by various methods. If such a crimp is not permanently set or stabilized, however, it gradually disappears as the fiber goes through various processing stages until the aforesaid advantages which crimp olfers are lost. If, particularly, a yarn or fabric whose crimp has not been set or stabilized is subjected to a wet thermal treatment, such as boiling or dyeing at the finishing stage of the production process, such a great part of the crimp is lost that the bulkiness, feeling, and hand of the yarn or fabric so treated will deteriorate in a considerable degree. This is the reason why the stability of crimp under hot humid conditions has an important implication.

It is known that crimp may be given a stability against moist heat by treating the fiber possessing such crimps with hot water or steam under ressure. However, since this pressure treatment requires specialized equipment, a need has existed for a method whereby crimp may be set more easily,

On the other hand, in the production of synthetic fiber for use as textile fabrics, it is generally considered necessary to stretch the fiber in order to give it added strength by orienting the chemical molecules forming the fiber in the direction of the fiber axis. In order to impart satisfactory physical and chemical properties to the fiber, however, it is necessary to cause the stretched fiber to shrink to a certain extent by treating it in a relaxed state. Relaxation of fiber improves not Only the knot strength and elongation but also the receptibility of the fiber to dyestuffs, besides the function of restraining the tendency of the fiber to degrade into fibrils. Conventionally, relaxation of fiber has been effected by various methods, which, for instance include a method comprising a treatment of fiber under hot dry conditions, a method wherein fiber is treated with water at elevated temperature and pressure or with steam under elevated pressure, and a method which comprises treating fiber with a dilute aqueous solution of a chemical compound which can dissolve fiber, i.e. a solvent for fiber. None of the methods just mentioned is completely satisfactory, however, for each has its own disadvantages. By way of illustration, the first-mentioned the solvent is too readily adsorbed by fiber to permit its easy removal after the treatment.

It is an object of the invention to provide an improved method for easily setting the crimps in fibers, yarn, or fabrics made of acrylonitrile type polymers under atmospheric pressure by eliminating the aforementioned disadvantages of conventional methods. It is another object of the invention to provide a method for relaxing fiber under atmospheric pressure wherein the shrinkage of fiber may be easily controlled and where the aforementioned disadvantages are absent.

We have found that the aforementioned drawbacks of the known methods may be avoided and, accordingly, fiber relaxed and stabilized very efficiently when the fiber is treated with acetonitrile, pyridine, or dioxane, and, more preferably, with an aqueous solution thereof or a vapor generated as it is boiled. Thus, in accordance with the invention, fiber may be successfully treated at a temperature of 100 C. or less under atmospheric pressure without the fear of discoloration and degradation, with an additional advantage that both the concentration and temperature can be so controlled as to yield a uniform degree of shrinkage. The method is particularly beneficial in that a more or less constant degree of shrinkage is assured over a substantially wide range of variations in the concentration of the treating agent whereby the degree of relaxation is substantially a function of temperature only.

The conditions under which the invention can be most successfully utilized in the relaxation or shrinking of fiber depend on the composition of the fiber and the desired properties of the resulting product. The relationship between treating conditions and the degrees of shrinkage of a fiber spun from a copolymer consisting of 90% acrylonitrile and 10% methyl acrylate is shown in FIGS. 1, 2 and 3, for example.

FIGURES 1, 2, and 3 are graphs showing the rates of shrinkage of such a fiber plotted as a function of concentration of aqueous solutions of acetonitrile, pyridine, and dioxane, respectively.

In each instance, the maximum point in the shrinkage curve as plotted against the concentration of the treating agent was reached in the neighbourhood of to percent. That maximum shrinkage occurs within this concentration range is surprising and quite unexpected and a satisfactory reason for this behavior is still to be elucidated.

When fiber is treated with aqueous solutions of known solvents for acrylonitrile type polymers, e.g. N,N-dimethylformamide, dimethylsulfoxide, 'y-butyrolactone, or ethylene carbonate, the shrinkage of the fiber increases consistently with increasing concentrations of solvents until, eventually, the fiber is completely dissolved. Thus, whenever such a solvent is employed, controlling of its concentration becomes a major problem in order to keep the shrinkage of fiber uniform. In contrast with the aforesaid practice, and in accordance with the present invention, the change in the degree of shrinkage with change in concentration of the treating agent is always so small when the fiber is treated near the concentration for maximum shrinkage that exact control of the concentration of the treating agent is not of great importance. Furthermore, when fiber is treated with vapor of the treating agents acetonitrile, pyridine, and dioxane are each capable of forming an azeotropic mixture with water with the result that when the actual concentration of the treating agent is reasonably near the azeotropic composition, a small change in concentration of the liquid does not affect the composition of the vapor generated therefrom upon boiling. The effect of this is to make it much easier to control the degree of shrinkage of the fibers being relaxed. This is apparently one of the outstanding features of the invention.

It has been found that the degree of shrinkage is a conjoint function of fiber composition, treating agent composition, and temperature. Generally speaking, greater shrinkages are produced at higher temperatures for a given fiber composition and treating agent composition. However, it has been found that it is undesirable to so elevate the temperature as to attempt shrinkages in excess of about 50% because of the danger of deleteriously affecting fiber or fabric. Thus, the preferred degree of shrinkage lies within the range of 1 to about 50 percent.

When the invention is utilized for the purpose of setting the crimp in fiber, it is preferable to treat the fiber in the vapor of said treating solution, or in the solution at a temperature not exceeding about 60 C.

It is also possible to carry out both the shrinking and crimp-setting of fiber concurrently. For this purpose, a fiber which has been preliminarily crimped by mechanical means may simply be treated under conditions which are conducive of crimp setting and which are, at the same time, capable of yielding the desired degree of shrinkage.

Besides regular fibers, this invention is also applicable 'to such multi-component fibers as may be characterized bythe cross-section of each monofilament showing two dissimilar acrylonitrile type polymers, and in this particular instance a natural crimp may be imparted to the fiber by causing the two components to shrink in different degrees. 1

In each of the aforementioned cases, the shrinkage of the fiber reaches an equilibrium when it has been treated for a certain period of time, and after this equilibrium is established, the shrinkage of fiber becomes independent of the treating time. Usually, the time which elapses before such an equilibrium is reached is less than five minutes. After this time, the increase, if any, in shrinkage will scarcely amount to more than 1 to 2 percent, and the shrinkage value remains practically constant. Stated differently, the degree of shrinkage depends on the composition of the treating agent and the temperature and is substantially independent of time after a certain period of times.

The fiber, yarn or fabric so treated is then washed free of the treating agent with water and finally dried.

The term acrylonitrile type polymers as used throughout this specification refers to those homopolymers, copolymers, graft polymers, or block polymers which contain 80 to 100 percent by weight of acrylonitrile, or any mixtures thereof. As the components which make up the rest of the composition, such a polymer as mentioned above may contain one or more of the widely known monoethylenic unsaturated compounds such as vinyl acetate, vinyl chloride, vinylidene chloride, styrene and its derivatives, acrylic acid and its esters, methacrylic acid and its esters, methacrylonitrile, vinylidene cyanide, methylvinyl ketone, vinyl pyridine and its derivatives, vinyl pyrrolidone, ethylenesulfonic acid, styrenesulfonic acid, allylsulfonic acid, methallysul-fonic acid and the like. Other examples of monomers which are copolymerizab-le with acrylonitrile to form fiber-forming polymers from which can be made fibers treatable in accordance with the present invention are given, for example, in US. Patent 2,874,446 (e .g. column 4, line 57 to column 5, line 12).

As denominations for expressing the effects obtainable by the treatment of fiber according to the invention, the degree of shrinkage, the crimp-number retentivity, and the crimping-degree retentivity are defined as follows:

length of fiber before treatment) X100 4 Crimp-number retentivity (percent) number of crimps after boiling in water for 10 min.

number of crimps in original fiber X 100 Number of crimps =number of crimps per 25 mm. length of a single fiber under 5 mg. load Degree of crimping l length of fiber under 5 mg. load )XlOO length of fiber under 150 mg. load This invention will be described in further detail hereinafter by way of examples, it being to be understood, however, that the invention is by no means limited thereto. (In the following examples, all quantities are by weight.)

Example 1 Three copolymers comprising acrylonitrile and methyl acrylate in the proportions of 90:10, 92:8, 95:5, respectively, were each extruded from an aqueous solution of sodium thiocyanate into a cold aqueous coagulating bath. The resulting filaments were stretched 2.5 times the initial length in air at room temperature and, then, 4.4 times in hot water, for a total stretch to 11 times the initial length. The stretched filaments were collapsed by drying at the relative humidity of 25% and the temperature of 105 C.

These filaments were immersed in aqueous solutions of acetonitrile at C. or 80 C. for 30 minutes, and the' degree of shrinkage of each fiber was measured. The results are summarized in Table 1.

The degree of shrinkage reached its peak in the neighborhood of acetonitrile, although the degree of shrinkage is fairly uniform from about 50% to about by weight of acetonitrile (i.e., about 20% to about 50 water). It is surprising to note that by using a mixture of acetonitrile and water a definitely greater shrinkage can be obtained than when either acetonitrile or water is separately employed and that a substantial shrinkage can be achieved at a temperature below that at which either material alone produces any appreciable shrinkage- Example 2 A copolymer comprising acrylonitrile, 10%

. methyl acrylate and 0.75% methallylsulfonic acid was processed into dried and collapsed filaments in the same manner as Example 1. The filaments were then immersed in aqueous solutions. of pyridine, and the degree of shrinkage of each fiber was measured. The results are summarized in Table 2.

, TABLE 2 Ooncentra- Treating time (minutes) Temp. tion of pyridine (percent) 5 10 20 30 80 C 25 2. 0 2. 2 2. 4 2. 5 50 5. l 5. 5 5. 7 5. 9 75 8. 2 8. 6 8. 8 9. 0 1. 0 1. 0 1. 0 1.0 100 C 25 8.8 9. 4 9.8 10. 0 50 16. 1 17. 4 1.9. 1 19. 2 75 22. 4 23. 2 24. 6 25. 2 100 3. 9 4. 8 5. 0 5. 2

The maximum degree of shrinkage was observed in the neighborhood of 75% pyridine, although the degree of shrinkage is fairly uniform from about 50% to about 80% by Weight of pyridine (i.e., from about 20% to about 50% with a vapor generated by boiling a 75% solution of pyridine for minutes, and (3) a third sample was used as a control. The yarn quality and the stability of crimp of each sample was measured and the results water). When the changes in the degree of shrinkage with 5 summarized in the following table.

TABLE 4 Dry Knot Percent Percent Number Degree of Crimp Crimping Sample Treating Shrinkage Denier strength strength ry Knot of crimps crimping number degree agent (percent) (g./d.) (g./d.) elongation elongation (erimps) (percent) retentivity retentivity (percent) (percent) Acetonitrile 16. 2 3. 08 3. 24 2. 56 66. 8 56. 6 10. 1 8. 7 80 127 Pyridine 16. 2 3.13 3. 52 2. 39 61. 7 61. 2 15. 5 8. 8 88 157 Control 0 2. 59 3. 51 2. 23 27. 4 19. 2 12. 2 8. 6 55 70 time was measured, it was found that the degree of shrinkage reached substantial equilibrium in about 5 minutes. After this time, the fibers show a further shrinkage of 3% at most and usually less than 1 to 2%.

Samples 1 and 2, which has been treated with aqueous acetonitrile and aqueous pyridine respectively, not only showed a shrinkage of about 16% but also had sufiicient elongation and improved knot strength values. The crimp Emmple 3 20 retentivity of the samples was also excellent having reached or exceeded 80%. In contrast, the control sample Three cQPOIYIIWTS 9 1 3! acryloflltnle and methyl 3 was inferior in both knot strength and elongation, with acrylate ill the PTQPortlons of 9218, 811d 9515, its crimp retentivity value being much lower than those spectively, were processed into dried and collapsed filaof h treated ments as in Example 1. The filaments were immersed in E I 5 aqueous solutions of dioxane for minutes and the dexamp e gree of shrinkage of each fiber was measured. The results A copolymer comprising 90% acrylonitrile and 10% are Summarlled 111 Table methyl acrylate was processed into a tow of collapsed TABLE 3 filaments as in Example 1. The tow was then fed to a 30 stufling box for crimping. Samples of the crimped fila- Concentra- Acrylonitn'leunethylacrylate(%) ments were treated with aqueous acetonitrile, aqueous Temppyridine, and aqueous dioxane respectively as indicated ercent) 9010 92;s 95:5 in Table 5. The yarn quality and crimp retentivity of each r sample are summarized in Table 5. 80 c 25 as 4.4 2.5 With respect to all examples from 1 to 5, the shrinkage g2 g1: g2 33 of fiber and the setting of its crimp were accomplished 100 4.6 2.9 0.6 concurrently. Samples 1 to 5 had their knot strength values considerably improved, with their elongation fig- TABLE 5 Dry Knot Percent Percent Number Degree of Cn'mp- Crimping- Sample Treatment Shrinkage Denier strength strength dry knot of crimpS crimping number degree (percent) (g./d.) (g./d.) elongaelonga- (crimps) (percent) retentivity retenttvity tron tion (percent) (percent) 1 solution of 25.0 3.29 2. 59 2.34 71.1 60.0 9.3 8.0 97 110 acetonitrile at 0. for 30 minutes. 2 Avapor of 75% 24.4 3. 05 3.13 2.68 50.9 44.3 10.2 0.0 124 131 pyridine at the boiling point for 30 minutes. 3 A vapor of 50% 22.1 2.95 3. 27 2.68 45. 7 39. 0 11.3 9. 8 104 108 pyridine at the boiling point for 30 minutes. 4 A vapor of 75% 24. 0 3.11 3.05 2. 57 52. 2 45. e 10. 4 10.4 104 11s dioxane at the boiling point for 30 minutes. 5 A vapor oi50% 19.8 2.94 3.15 2.67 40.0 30.4 9.9 10.6 89 91 dioxane at the boiling point for 30 minutes. 6 Control 0 2.35 4.34 1.41 22.9 5.6 10.5 12,3 53 33 In the case of dioxane, the maximum shrinkage ocures also having been substantially improved by the recurred in the neighbourhood of 75%, and around this spective treatments. It is also apparent from the retentivity Concentration (from about 50% 10 about dloxan'e) figures for both the number of crimps and the degree of there was little change in the degree of shrinkage with crimping (which are about 100%) that the crimp will Change 111 concisntrat10nnot be removed if the samples are boiled in water.

Example 4 Example 6 A copolymer comprising 90% acrylonitrile, 10% methyl acrylate and 0.75% methallylsulfonic acid was g g g gggs j g z fi gg g z gfg i z processed into a dried and collapsed tow as in Example 1. 906 d 95x51) 75 l P p u The tow was preliminarily heated in hot water at C. an Fespecnve y were y and fed to a stufling box for crimping Samples of the extruded into a tow of bi-component filaments, which crimped tow were treated in the f ll i manner; 1) were then stretched and collapsed. The resulting collapsed a Sampk: was immersed in a 50% l i f t it ile bl-component filaments developed natural crimp when at 55 C. for 20 minutes, (2) another sample was treated 75 they were immersed 1n a 50% aqueous solution of aceto- 7 nitrile at 60 C. for minutes. The yarn quality of the filaments are summarized in Table 6.

TABLE 6 Degree of shrinkage percent 18.7 Denier 2.87 Dry strength g./d 3.52. Knot strength g./d 2.95 Dry elongation percent 50.3 Knot elongation do 47.3 Number'of crimps 9.1 Degree of crimping percent 12.7

Example 7 A copolymer comprising 90% acrylonitrile and 10% methyl acrylate was processed into collapsed filaments as in Example 1. Samples of the filaments were immersed in aqueous solutions of N,N-dirnethylformamide, di-

methylsulfoxide and 'y-butyrolactone, respectively, for 30 minutes, and the degree of shrinkage of each sample was measured. When these acrylonitrile polymer solvents are employed, the degree of shrinkage increased rather sharply with increasing concentration until the fiber was dissolved. Since a small change in concentration results in a substantial change in shrinkage, it is diiiicult to treat a tow having a great total denier in any uniform pattern. It is also difficult to obtain a degree of shrinkage which approximates the desired value.

We claim: a

1. The method of relaxing dried filamentary material comprising a polymer containing at least 80% by weight of acrylonitrile, said method comprising treating the said dried filamentary material with a treatment material selected from the group consisting of aqueous acetonitrile, aqueous pyridine, and aqueous dioxane containing from 20% to by weight of water at an elevated temperature below that at which about 50% shrirkage occurs.

2. The method as defined in claim 1 wherein the treatment material comprises an azeotropic mixture.

3. The method as defined in claim 1 wherein the filamentary material is treated with the treatment material as an aqueous solution.

4. The method as defined in claim mentary material is treated with the treatment material as a vapor.

5. The method as defined in claim 1 wherein the treatment material contains about 25% water.

6. The method as defined in claim 1 wherein the treatment material is aqueous acetonitrile.

7. The method as defined in claim 1 wherein the treatment material is aqueous pyridine.

-8. The method as defined in claim 1 wherein the treatment material is aqueous dioxane.

References Cited UNITED STATES PATENTS 3/1963 Wishman 8130.1 5/1954 Hare et al. 8-1301 OTHER REFERENCES NORMAN G. TORCHIN, Primary Examiner.

I. C. CANNON, Assistant Examiner.

1 wherein the fila- 

1. THE METHOD OF RELAXING DRIED FILAMENTARY MATERIAL COMPRISING A POLYMER CONTAINING AT LEAST 80% BY WEIGHT OF ACRYLONITRILE, SAID METHOD COMPRISING TREATING THE SAID DRIED FILAMENTARY MATERIAL WITH A TREATMENT MATERIAL SELECTED FROM THE GROUP CONSISTING OF AQUEOUS ACETONITRILE, AQEUOUS PYRIDINE, AND AQUEOUS DIOXANE CONTAINING FROM 20% TO 50% BY WEIGHT OF WATER AT AN ELEVATED TEMPERATURE BELOW THAT AT WHICH ABOUT 50% SHRINKAGE OCCURS. 